105 Radio/Serial Telemetry Module
User Manual
Page
18
©
January 2004
resistance of less than 250 ohms and zener diode protection is provided against over-voltage and
reverse voltage, however additional protection may be required in high voltage or noisy
environments or for very long wiring runs.
A 24VDC loop supply is available on the 105 module for powering the analogue transducer loops.
In this case, the analogue loop should be connected between a "AI 1-" terminal and "COM" ( for
the first analogue input) or "AI 2-" ( for the second analogue input), and so on for other inputs. The
positive terminal ("AI 1+" or "AI 2+", etc) should be connected to "+24V".
Externally powered loops may be connected by connecting the input between "AI 1+" and “AI 1-”
for analogue input 1 or "AI 2+" and “AI 2-” for analogue input 2, and so on for other inputs.
Common mode voltage may be -0.5V to 27V.
Shielded cable is recommended for analogue I/O loops to minimise induced noise and Radio
Frequency Interference (RFI). The shield of the cable should be connected to earth at one of the
cable only. The use of shielded wiring inside an enclosure containing a 105 module is also
recommended.
To connect an AI on the 105U to an analogue signal from a PLC or DCS output, check the internal
circuit of the output carefully as different devices use different ways to create an analogue signal.
The following diagram shows two ways of connecting.
2.4.5
Analogue Outputs (105-1 and 105-3)
The 105-1 module provides two 4 - 20 mA DC analogue outputs for connecting to instrument
indicators for the display of remote analogue measurements. The 105-3 module provides eight 0 -
20 mA DC analogue outputs. Each analogue output is a "sink" to common.
A 24VDC supply is available on the 105 module for powering the analogue output loop (max
external loop resistance 1000 ohms). In this case, the analogue loop is connected between a "+24V"
terminal and "AO 1" ( for the first analogue output) or "AO 2" (for the second analogue output),
and so on for the other output signals.
If connecting to an external device such as an electronic indicator, recorder or PLC / DCS input,
AO
PLC
_
+24V
+AI
- AI
COM
105U
+24V
+AI
- AI
COM
105U
Current
source
output
Note:
1. AI must be within
27V of COM. If
terminal voltages
exceed this, a loop
isolator must be
used.
2. COM on the
105U is connected
to ground/earth. If
the COM of the
PLC cannot be
grounded, then a
loop isolator must
be used.
+
+
V
-
V
AO
COM
PLC
Current
sink
output
